1. Field of the Invention
This invention relates to an image forming apparatus with a supplemental power supply unit. The supplemental power supply unit supplies the DC power to a plurality of DC-powered units of the image forming apparatus during the predetermined period and enables to increase the AC power to the heater for fixation.
2. Discussion of the Background
An image forming apparatus like a copy, a printer, and a facsimile using an electrophotographic technology usually has a fusing unit to fix a toner image on a recording sheet to the recording sheet. The fusing unit is provided with a pair of rollers, a heater in at least one of the rollers and the controller that controls the heater on off in order to maintain a temperature of the roller.
The image forming apparatus is required to be able to print in a short time after the image forming apparatus is turned on or recovered from a power saving mode. Generally, the most important factor to achieve the fast recovery is to minimize a warm up time, which is the time that the temperature of the roller rises to a fusing temperature at the power on sequence, and a recovery time, which is the time that the temperature of the roller rises to the fusing temperature at the recovery sequence from the power saving mode.
Recently, the image forming apparatus is usually connected to the external device, like a PC, and is always turned on, therefore shortening the recovery time from the power saving mode is considered very important.
In order to achieve a fast recovery, supplying much power to the fusing unit is one of solutions but the power, which can obtain from the AC outlet, is strictly limited by the law.
In Japanese Open-Laid Patent 2004-236492, the image forming apparatus, which has a supplemental power supply unit (PSU) and supplies DC power to the image forming apparatus from the supplemental PSU when the total amount of DC power consumption is predicted to exceed the limit, is disclosed. This type of image forming apparatus can equalize the power consumption, but do not aim to provide fast recovery.